Environmental Engineering Reference
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and yield stress has a significant impact on the final results. Only after
4-5 ranges counted in the calculation, can the results be regarded as final
and differing only slightly. This is especially important when the so-called
guaranteed values of mechanical properties, listed in the re
gu
lations, are
used. For the yield stress this usually corresponds to
(
)
s−s
.
Example
. It is required to determine the probability of brittle fracture
of a structure which contains discontinuities, and its dependence on various
characteristics
96
and section 5.3.5.
Input data
:
K
1
c
min
= 259.9; ¯
1
c
= 356.5;
D
0.5
T
T
K
1
c
= 48.3 - the crack
characteristics; σ
max
= 26.9;
D
0.5
= 0.05; ¯ = 26.8 - the stress characteristics;
a
max
= 48.12;
a
0
= 3.19; γ = 0.307 - the defect characteristics.
Figures 5.52-5.56 show the dependences of the probability of failure
on different characteristics.
For the input data ¯
1
c
= 356.5;
D
0.5
σ
= 2;
a
max
= 48.12;
f
= 1;
a
0
= 3.19; γ = 0.307 calculations yielded the graphical
dependences shown in Fig. 5.57-5.59.
K
1
c
= 48.6; ¯ = 26.8;
D
0.5
5.52
Dependence of probability of failure on
D
K1c
0.5
.
5.3.7 Changes in strength properties of steels in
operation due to ageing
The generalised model delas with different types of ageing. Ageing in the
form of growth of defects during operation is taken into account by the
methods described in sections 4.1, 5.3.3 and 5.3.4. Ageing as thinning of
the walls of equipment by corrosion is taken into account by substituting
the stress, taking into account the new size and shape of the structure.
Ageing as a change in the mechanical properties during operation was
studied by experimental studies of the properties of metal cut from the
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